This is a genuine, live disagreement in the evidence. Both sides below are independently sourced and graded — read the grades, not just the labels.
Some real trials report a benefit
Several smaller randomized trials report reduced hot flash frequency and severity with black cohosh compared to placebo, including benefit shown for tamoxifen-associated hot flashes in breast cancer patients.
Early, limited, mixed, or indirect research. Some people may find this useful, but we can't be confident about the average effect.
What does this grade mean?The largest, most rigorous trial found no effect
The HALT trial — a large, multi-site randomized trial of 351 perimenopausal women — found black cohosh no more effective than placebo, consistent with a 2012 Cochrane review of 16 RCTs (2,027 women) and NAMS's own "not recommended" position.
There is reasonably consistent research, but important limitations or unanswered questions remain.